Thanks for the contacting Syncfusion support.
Before proceeding on your query, could you please check the below query regarding your requirement and address them.
1. Are you expecting to apply filter from parent grid to the child grid in details row. For example, when parent grid is filtered with EmployeeID equal to 5 then are you expecting the child grid to apply this same filter criteria to its data.
2. Share your grid code to understand the parent and child grid column schema.
3. Does the parent grid filter has to be done using filter UI or programmatically.
Madhu Sudhanan P